Air conditioning system and control method

ABSTRACT

A cooling and dehumidification system including at least one passive heat transfer device with desiccant coated on some extent of the exposed surface, another passive heat transfer device without desiccant coating, a compressor through which refrigerant flows, an expansion device, a refrigerant control valve, and valves to direct airflow in relation to the passive heat transfer devices.

RELATED APPLICATION

This application claims the benefit of co-pending U.S. ProvisionalApplication Ser. No. 63/184,070, entitled AIR CONDITIONING SYSTEM ANDCONTROL METHOD, filed May 4, 2021, the teaching of which are expresslyincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to system and method to provide coolingand dehumidification to a space.

BACKGROUND OF THE INVENTION

The rising demand for cooling is putting an enormous strain on theenvironment, grid infrastructure, and the global climate. Meeting theworld's demand for cooling while minimizing its negative impacts will beone of the defining challenges of our time. This challenge can beaddressed by redesigning today's air conditioning systems to takeadvantage of new materials and chemical processes.

Conventional vapor-compression based air conditioning systems providecooling and dehumidification by passing air over a cooling coil. Thecoil is maintained at a lower temperature than the air by the flow ofrefrigerant through the coil. Sensible cooling is achieved by passingair over a cooling coil which is cooler than the entering air, resultingin heat transfer from the air to the refrigerant and reducing thetemperature of the air. Latent cooling, or dehumidification, is achievedby passing air over a cooling coil which is below the dewpoint of theentering air. This results in moisture from the air forming condensateon the coil surface and transferring the latent heat of vaporization tothe refrigerant. In such systems, sensible and latent heat removal arecoupled such that either sensible or latent cooling can be controlled,but not both. Furthermore, to meet high latent loads the cooling coilmust operate at very low temperatures, resulting in poor efficiency ofthe vapor compression system.

SUMMARY OF THE INVENTION

The present disclosure overcomes the disadvantages of the prior art byproviding a cooling and dehumidification system, comprising: at leastone passive heat transfer device with desiccant coated on some extent ofthe exposed surface, another passive heat transfer device withoutdesiccant coating, a compressor through which refrigerant flows, anexpansion device, a refrigerant control valve, and valves to directairflow in relation to the passive heat transfer devices.

In and illustrative embodiment, An air-handling system and methodcomprises a heat pump configured to move heat energy between a pluralityof passive heat transfer devices. The plurality of passive heat transferdevices, define a first surface of at least one of the plurality ofpassive heat transfer devices that is thermally in contact with the heatpump, and a second surface of at least one of the plurality of passiveheat transfer devices that is exposed to allow the transfer of heat toor from the heat pump. A desiccant can be in thermal contact with theexposed surface of at least one passive heat transfer device andconfigured to exchange moisture with air. A plurality of air directingvalves are configured to direct process and regeneration air to and fromthe plurality of passive heat transfer devices with desiccant. A heatpump reversing device can be configured to change the direction of heatflow in the heat pump between two modes of operation, and a controlsystem with communication lines can control air directing valves,reversing device, and heat pump operation. A control operation processcan operate a control mode in which desiccant regeneration time ismodulated. Illustratively, the passive heat transfer devices cancomprise tube and fin heat exchangers or microchannel heat exchangers.The desiccant can form a coating on the exposed surface of the heatexchanger fins, which can be a partial coating with an uncoated sectionfirst exposed to airflow followed by a desiccant coated second sectionexposed to airflow. A passive heat transfer device without desiccant canbe configured for exchanging sensible heat with ambient air, and/or thepassive heat transfer device without desiccant can be configured forexchanging sensible heat with indoor air. The desiccant can comprise anyacceptable material, or combination of materials, including at least oneof silica gel, alumina, zeolite or a metal-organic framework (MOF)material.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention description below refers to the accompanying drawings, ofwhich:

FIG. 1A depicts a cooling and dehumidification system with two desiccantcoated passive heat transfer devices and a third uncoated passive heattransfer device in a first mode of operation.

FIG. 1B depicts a cooling and dehumidification system with two desiccantcoated passive heat transfer devices and a third uncoated passive heattransfer device in a second mode of operation.

FIG. 2A depicts a cooling and dehumidification system with two desiccantcoated passive heat transfer devices and a third uncoated passive heattransfer device in a first mode of operation.

FIG. 2B depicts a cooling and dehumidification system with two desiccantcoated passive heat transfer devices and a third uncoated passive heattransfer device in a second mode of operation.

FIG. 3A depicts a cooling and dehumidification system with one desiccantcoated passive heat transfer device and two uncoated passive heattransfer devices in a first mode of operation.

FIG. 3B depicts a cooling and dehumidification system with one desiccantcoated passive heat transfer device and two uncoated passive heattransfer devices in a second mode of operation.

FIG. 4A depicts a cooling and dehumidification system with two desiccantcoated passive heat transfer devices in a first mode of operation.

FIG. 4B depicts a cooling and dehumidification system with two desiccantcoated passive heat transfer devices in a second mode of operation.

FIGS. 5A-5D depict embodiments of a refrigerant flow and metering devicein two modes of operation.

FIG. 6A depicts a cross sectional view of an embodiment of an indoorcooling and dehumidifying device in a first mode of operation.

FIG. 6B depicts a cross sectional view of an embodiment of an indoorcooling and dehumidifying device in a second mode of operation.

FIG. 7 depicts a method of control for a desiccant cooling anddehumidification system.

DETAILED DESCRIPTION

FIGS. 1A and 1B show schematic views of an exemplary desiccant coolingand dehumidification system 100. In operation, system 100 cycles betweentwo modes of operation: a first mode (also referred to as a firsthalf-cycle), and a second mode (also referred to as a secondhalf-cycle). FIG. 1A illustrates the first mode of operation and 1Billustrates the second mode of operation. System 100 includes a heatpump comprising compressor 103, uncoated (i.e., free of desiccantmaterial) passive heat transfer device 104, refrigerant reversing valve105, a first desiccant coated passive heat transfer device 107,expansion valve 108, and a second desiccant coated passive heat transferdevice 109. System 100 further includes first air directing valve 113,second air directing valve 114, and first fan 115. System 100 furtherincludes first air duct 119, third air directing valve 120, fourth airdirecting valve 121, second fan 122, and second air duct 123. System 100further includes third fan 128.

As shown in the example of FIGS. 1A and 1B, compressor 103, uncoatedpassive heat transfer device 104, refrigerant reversing valve 105 andfan 128 are located outside of the conditioned space within one or morehousing structures and form outdoor device 102. Desiccant coated passiveheat transfer devices 107 and 109, air directing valves 113, 114, 120,and 121, fans 115 and 122, and expansion valve 108 are located insidethe conditioned space in one or more housing structures and form indoordevice 101. The indoor space and outdoor space are separated by dividingwall 125. Indoor device 101 and the outdoor device 102 are thermallyconnected through refrigerant lines 106 and 110 that pass through thedividing wall 125. Furthermore, indoor device 101 is physicallyconnected to air ducts 113 and 118 which pass through dividing wall 125to the outdoor space.

System 100 operates in a cyclic manner, alternating between two modes ofoperation, shown by FIGS. 1A and 1B. During the first half-cycle,desiccant coated passive heat transfer device 109 is in process mode anddesiccant coated passive heat transfer device 107 is in regenerationmode. During the second half-cycle, the roles of desiccant coatedpassive heat transfer device 109 and desiccant coated passive heattransfer device 107 reverse such that desiccant coated passive heattransfer device 109 is in regeneration mode and desiccant coated passiveheat transfer device 107 is in process mode.

By way of non-limiting example, the desiccant can comprise anyappropriate material clear to those of skill, which is designed tocapture moisture using a desiccant material such as a silica gel,alumina, zeolite or a metal-organic framework (MOF) material. Thedesiccant media comprising a plurality of desiccant structures can bemanufactured/applied, based upon known techniques and equipment, forexample, using a composite material that consists of the activedesiccant powder embedded within a rigid binding material such as aceramic or plastic that does not affect the desiccant material's abilityto adsorb moisture. Such is applied to the heat exchanger usingconventional coating or layering techniques, or is otherwise applied to,e.g. fins of the heat exchange element.

FIG. 1A shows the first half-cycle of operation of system 100.Low-pressure refrigerant at a first pressure state enters compressor 103and is compressed to a second pressure state (e.g., high-pressure state)that is higher than the first pressure state. Refrigerant then flowsthrough uncoated passive heat transfer device 104, releasing some heatto ambient airstream 126. Refrigerant then flows through refrigerantreversing valve 105 (configured in a first valve state) and is directedto refrigerant line 106. Refrigerant then flows through refrigerant line106 from outdoor device 102 to indoor device 101. Refrigerant then flowsthrough desiccant coated passive heat transfer device 107, releasingsome heat to regeneration airstream 118. Refrigerant then flows throughexpansion valve 108 which takes the refrigerant from a high-pressurestate to a low-pressure state. Refrigerant then flows through desiccantcoated passive heat transfer device 109 absorbing some heat from processair 111. Refrigerant then flows through refrigerant line 110 from indoordevice 101 to outdoor device 102. Refrigerant then flows throughreversing valve 105 (in the first valve state) and back to compressor103, completing the circuit.

Process air 111 to be cooled and dehumidified enters indoor device 101through air inlet 112 and is directed by air directing valve 113 todesiccant coated passive heat transfer device 109. Process air passesover the exposed surface of desiccant coated passive heat transferdevice 109, cooling and dehumidifying the air. Moisture from the air isadsorbed onto the desiccant, increasing the moisture content of thedesiccant. The heat of adsorption from the desiccant is transferred topassive heat transfer device 109 by conduction, and to the refrigerantflowing through. Sensible heat from the process airstream is alsotransferred to passive heat transfer device 109 and to the refrigerantflowing through. The cooled and dehumidified air is then drawn throughair directing valve 114 by process fan 115, and passes through airoutlet 116 to the conditioned space 117.

Regeneration air 118 enters indoor device 101 through inlet duct 119 andis directed by air directing valve 120 to desiccant coated passive heattransfer device 107. Regeneration air passes over the exposed surface ofdesiccant coated passive heat transfer device 107. Heat passes from therefrigerant to passive heat transfer device 107, and on to thedesiccant, causing desorption of moisture from the desiccant to thepassing air. In this way the desiccant is regenerated to begin the nextcycle. Regeneration air is then drawn through air directing valve 121 byfan 122 and through outlet duct 123 to the outdoor space 124.

Ambient air 126 from the environment enters outdoor device 102 throughinlet 127. Air passes over the exposed surface of passive heat transferdevice 104. Heat passes from the refrigerant to passive heat transferdevice 104, and from passive heat transfer device 104 to the air. Air isdrawn by fan 128 from passive heat transfer device 104 through outlet129 and back to the outdoor space 130.

FIG. 1B shows the second half-cycle of operation of system 100.Low-pressure refrigerant at a first pressure state enters compressor 103and is compressed to a second pressure state (e.g., high-pressure state)that is higher than the first pressure state. Refrigerant then flowsthrough uncoated passive heat transfer device 104, releasing some heatto ambient airstream 126. Refrigerant then flows through refrigerantreversing valve 105 (configured in a second valve state) and is directedto refrigerant line 110. Refrigerant then flows through refrigerant line110 from outdoor device 102 to indoor device 101. Refrigerant then flowsthrough desiccant coated passive heat transfer device 109, releasingsome heat to regeneration airstream 118. Refrigerant then flows throughexpansion valve 108 which takes the refrigerant from a high-pressurestate to a low-pressure state. Refrigerant then flows through desiccantcoated passive heat transfer device 107 absorbing some heat from processair 111. Refrigerant then flows through refrigerant line 106 from indoordevice 101 to outdoor device 102. Refrigerant then flows throughreversing valve 105 (in the second valve state) and back to compressor103, completing the circuit.

Process air 111 to be cooled and dehumidified enters indoor device 101through air inlet 112 and is directed by air directing valve 113 todesiccant coated passive heat transfer device 107. Process air passesover the exposed surface of desiccant coated passive heat transferdevice 107, cooling and dehumidifying the air. Moisture from the air isadsorbed onto the desiccant, increasing the moisture content of thedesiccant. The heat of adsorption from the desiccant is transferred topassive heat transfer device 107 by conduction, and to the refrigerantflowing through. Sensible heat from the process airstream is alsotransferred to passive heat transfer device 107 and to the refrigerantflowing through. The cooled and dehumidified air is then drawn throughair directing valve 114 by process fan 115, and passes through airoutlet 116 to the conditioned space 117.

Regeneration air 118 enters indoor device 101 through inlet duct 119 andis directed by air directing valve 120 to desiccant coated passive heattransfer device 109. Regeneration air passes over the exposed surface ofdesiccant coated passive heat transfer device 109. Heat passes from therefrigerant to passive heat transfer device 109, and on to thedesiccant, causing desorption of moisture from the desiccant to thepassing air. In this way the desiccant is regenerated to begin the nextcycle. Regeneration air is drawn through air directing valve 121 by fan122 and through outlet duct 123 to the outdoor space 124.

Ambient air 126 from the environment enters outdoor device 102 throughinlet 127. Air passes over the exposed surface of passive heat transferdevice 104. Heat passes from the refrigerant to passive heat transferdevice 104, and from passive heat transfer device 104 to the air. Air isdrawn by fan 128 from passive heat transfer device 104 through outlet129 and back to the outdoor space 130.

In some embodiments of system 100, a common fan is used to perform thefunctions of fans 115 and 122. In some embodiments of system 100, fan122 may be placed at any other location along the airflow path between118 and 124, similarly fan 115 may be placed at any other location alongthe airflow path between 111 and 117.

FIGS. 2A and 2B show schematic views of an exemplary desiccant coolingand dehumidification system 200. In operation, system 200 cycles betweentwo modes of operation: a first mode (also referred to as a firsthalf-cycle), and a second mode (also referred to as an a secondhalf-cycle). FIG. 2A illustrates the first mode of operation and 2Billustrates the second mode of operation. System 200 includes a heatpump comprising compressor 203, uncoated passive heat transfer device209, refrigerant reversing valve 204, a first desiccant coated passiveheat transfer device 206, refrigerant flow directing and metering device208, and a second desiccant coated passive heat transfer device 211.System 200 further includes first air directing valve 215, second airdirecting valve 216, and first fan 217. System 200 further includesfirst air duct 221, third air directing valve 222, fourth air directingvalve 223, second fan 224, and second air duct 225. System 200 furtherincludes third fan 230.

As shown in the example of FIGS. 2A and 2B, compressor 203, uncoatedpassive heat transfer device 209, refrigerant flow directing andmetering device 208, refrigerant reversing valve 204 and fan 230 arelocated outside of the conditioned space within one or more housingstructures and form outdoor device 202. Desiccant coated passive heattransfer devices 206 and 211, air directing valves 215, 216, 222, and223, and fans 217 and 224 are located inside the conditioned spacewithin one or more housing structures and form indoor device 201. Theindoor space and outdoor space are separated by dividing wall 227.Indoor device 201 and outdoor device 202 are thermally connected throughrefrigerant lines 205, 207, 210, and 212 that pass through the dividingwall 227. Furthermore, indoor device 201 is physically connected to airducts 221 and 225 which pass through dividing wall 227 to the outdoorspace.

System 200 operates in a cyclic manner, alternating between two modes ofoperation, shown by FIGS. 2A and 2B. During the first half-cycle,desiccant coated passive heat transfer device 211 is in process mode anddesiccant coated passive heat transfer device 206 is in regenerationmode. During the second half-cycle, desiccant coated passive heattransfer device 211 and desiccant coated passive heat transfer device206 reverse such that desiccant coated passive heat transfer device 211is in regeneration mode mode and desiccant coated passive heat transferdevice 206 is in process mode. In both modes, refrigerant flow directingand metering device 208 passes high pressure refrigerant first throughuncoated passive heat transfer device 209 and then through an expansionvalve contained therein. FIG. 3 shows possible embodiments ofrefrigerant flow directing and metering device 208.

FIG. 2A shows the first half-cycle of operation of system 200.Low-pressure refrigerant at a first pressure state enters compressor 203and is compressed to a second pressure state (e.g., high-pressure state)that is higher than the first pressure state. Refrigerant then flowsthrough refrigerant reversing valve 204 (configured in a first valvestate) and is directed to refrigerant line 205. Refrigerant then flowsthrough refrigerant line 205 from outdoor device 202 to indoor device201. Refrigerant then flows through desiccant coated passive heattransfer device 206, releasing some heat to regeneration airstream 220.Refrigerant then flows through refrigerant line 207 from indoor device201 to outdoor device 202. Refrigerant then flows through refrigerantflow directing and metering device 208 to uncoated passive heat transferdevice 209 releasing some heat to ambient airstream 228 and then throughan expansion valve in refrigerant flow directing and metering device208. Refrigerant then flows through refrigerant line 210 from outdoordevice 202 to indoor device 201. Refrigerant then flows throughdesiccant coated passive heat transfer device 211, absorbing some heatfrom process air 213. Refrigerant then flows through refrigerant line212 from indoor device 201 to outdoor device 202. Refrigerant then flowsthrough reversing valve 204 (in the first valve state) and back tocompressor 203, completing the circuit.

Process air 213 to be cooled and dehumidified enters indoor device 201through air inlet 214 and is directed by air directing valve 215 todesiccant coated passive heat transfer device 211. Process air passesover the exposed surface of desiccant coated passive heat transferdevice 211, cooling and dehumidifying the air. Moisture from the air isadsorbed onto the desiccant, increasing the moisture content of thedesiccant. The heat of adsorption from the desiccant is transferred topassive heat transfer device 211 by conduction, and to the refrigerantflowing through. Sensible heat from the process airstream is alsotransferred to passive heat transfer device 211 and to the refrigerantflowing through. The cooled and dehumidified air is then drawn throughair directing valve 216 by process fan 217, and passes through airoutlet 218 to the conditioned space 219.

Regeneration air 220 enters indoor device 201 through inlet duct 221 andis directed by air directing valve 222 to desiccant coated passive heattransfer device 206. Regeneration air passes over the exposed surface ofdesiccant coated passive heat transfer device 206. Heat passes from therefrigerant to passive heat transfer device 206, and on to thedesiccant, causing desorption of moisture from the desiccant to thepassing air. In this way the desiccant is regenerated to begin the nextcycle. Regeneration air is then drawn through air directing valve 223 byfan 224 and through outlet duct 225 to the outdoor space 226.

Ambient air 228 from the environment enters outdoor device 202 throughinlet 229. Air passes over the exposed surface of passive heat transferdevice 209. Heat passes from the refrigerant to passive heat transferdevice 209, and from passive heat transfer device 209 to the air. Air isdrawn by fan 230 from passive heat transfer device 209 through outlet231 and back to the outdoor space 232.

FIG. 2B shows the second half-cycle of operation of system 200.Low-pressure refrigerant at a first pressure state enters compressor 203and is compressed to a second pressure state (e.g., high-pressure state)that is higher than the first pressure state. Refrigerant then flowsthrough refrigerant reversing valve 204 (configured in a second valvestate) and is directed to refrigerant line 212. Refrigerant then flowsthrough refrigerant line 212 from outdoor device 202 to indoor device201. Refrigerant then flows through desiccant coated passive heattransfer device 211, releasing some heat to regeneration airstream 220.Refrigerant then flows through refrigerant line 210 from indoor device201 to outdoor device 202. Refrigerant then flows through refrigerantflow directing and metering device 208 to uncoated passive heat transferdevice 209 releasing some heat to ambient airstream 228 and then throughan expansion valve in refrigerant flow directing and metering device208. Refrigerant then flows through refrigerant line 207 from outdoordevice 202 to indoor device 201. Refrigerant then flows throughdesiccant coated passive heat transfer device 206, absorbing some heatfrom process air 213. Refrigerant then flows through refrigerant line205 from indoor device 201 to outdoor device 202. Refrigerant then flowsthrough reversing valve 204 (in the second valve state) and back tocompressor 203, completing the circuit.

Process air 213 to be cooled and dehumidified enters indoor device 201through air inlet 214 and is directed by air directing valve 215 todesiccant coated passive heat transfer device 206. Process air passesover the exposed surface of desiccant coated passive heat transferdevice 206, cooling and dehumidifying the air. Moisture from the air isadsorbed onto the desiccant, increasing the moisture content of thedesiccant. The heat of adsorption from the desiccant is transferred topassive heat transfer device 206 by conduction, and to the refrigerantflowing through. Sensible heat from the process airstream is alsotransferred to passive heat transfer device 206 and to the refrigerantflowing through. The cooled and dehumidified air is then drawn throughair directing valve 216 by process fan 217, and passes through airoutlet 218 to the conditioned space 219.

Regeneration air 220 enters indoor device 201 through inlet duct 221 andis directed by air directing valve 222 to desiccant coated passive heattransfer device 211. Regeneration air passes over the exposed surface ofdesiccant coated passive heat transfer device 211. Heat passes from therefrigerant to passive heat transfer device 211, and on to thedesiccant, causing desorption of moisture from the desiccant to thepassing air. In this way the desiccant is regenerated to begin the nextcycle. Regeneration air is then drawn through air directing valve 223 byfan 224 and through outlet duct 225 to the outdoor space 226.

Ambient air 228 from the environment enters outdoor device 202 throughinlet 229. Air passes over the exposed surface of passive heat transferdevice 209. Heat passes from the refrigerant to passive heat transferdevice 209, and from passive heat transfer device 209 to the air. Air isdrawn by fan 230 from passive heat transfer device 209 through outlet231 and back to the outdoor space 232.

In some embodiments of system 200, refrigerant flow directing andmetering device 208 is located within indoor device 201 instead ofoutdoor device 202.

In some embodiments of systems 100 and 200 the air switching valves arearranged in an alternative configuration such that two inlet air valvesare arranged to select between return air from the conditioned space andoutside air through an inlet air duct. Furthermore two exit valves arearranged to select between the conditioned space supply duct and tooutside air through an exhaust air duct. In this embodiment eachdesiccant coated passive heat transfer device is associated with asingle inlet air valve and a single exit air valve.

FIGS. 3A and 3B show schematic views of an exemplary desiccant coolingand dehumidification system 300. In operation, system 300 cycles betweentwo modes of operation: a first mode (also referred to as a firsthalf-cycle), and a second mode (also referred to as an a secondhalf-cycle). FIG. 3A illustrates the first mode of operation and 3Billustrates the second mode of operation. System 300 includes a heatpump comprising compressor 304, uncoated passive heat transfer device305, refrigerant reversing valve 307, desiccant coated passive heattransfer device 320, expansion valve 308, and a second uncoated passiveheat transfer device 310. System 300 further includes first airdirecting valve 319, second air directing valve 322, and first fan 321.System 300 further includes air ducts 331 and 332, second fan 327, andthird fan 314.

As shown in the example of FIGS. 3A and 3B, compressor 304, uncoatedpassive heat transfer device 305, and fan 327 are located outside of theconditioned space within one or more housing structures and form outdoordevice 303. Desiccant coated passive heat transfer device 320, airdirecting valves 319, and 322, fan 321, reversing valve 307, andexpansion valve 308 are located inside the conditioned space in one ormore housing structures and form indoor device 302. Uncoated passiveheat transfer device 310 and fan 314 are located inside the conditionedspace in one or more housing structures and form indoor device 301. Theindoor space and outdoor space are separated by dividing wall 334.Indoor device 301 is thermally connected to indoor device 302 throughrefrigerant line 335. Indoor device 301 is thermally connected tooutdoor device 303 through refrigerant line 311 that passes through thedividing wall 334. Indoor device 302 is thermally connected to outdoordevice 303 through refrigerant line 306 that passes through the dividingwall 334. Furthermore, indoor device 302 is physically connected to airducts 331 and 332 which pass through dividing wall 334 to the outdoorspace.

System 300 operates in a cyclic manner, alternating between two modes ofoperation, shown by FIGS. 3A and 3B. During the first half-cycle,desiccant coated passive heat transfer device 320 is in process mode.During the second half-cycle, desiccant coated passive heat transferdevice 320 is in regeneration mode.

FIG. 3A shows the first half-cycle of operation of system 300.Low-pressure refrigerant at a first pressure state enters compressor 304and is compressed to a second pressure state (e.g., high-pressure state)that is higher than the first pressure state. Refrigerant then flowsthrough uncoated passive heat transfer device 305, releasing some heatto ambient airstream 325. Refrigerant then flows through refrigerantline 306 from outdoor device 303 to indoor device 302. Refrigerant thenflows through reversing valve 307 (configured in a first valve state)and is directed to expansion valve 308, which takes the refrigerant froma high-pressure state to a low-pressure state. Refrigerant then flowsthrough desiccant coated passive heat transfer device 320 absorbing someheat from process air 317. Refrigerant then flows through reversingvalve 307 (in the first valve state) and is directed to refrigerant line335. Refrigerant flows through refrigerant line 335 from indoor device302 to indoor device 301. Refrigerant then flows through uncoatedpassive heat transfer device 310 absorbing heat from process air 312.Refrigerant then flows through refrigerant line 311 from indoor device301 to outdoor device 303 and returns to compressor 304, completing therefrigerant circuit.

Process air 312 to be cooled enters indoor device 301 through air inlet313 and passes over the exposed surface of uncoated passive heattransfer device 310, cooling the air.

Process air 317 to be cooled and dehumidified enters indoor device 302through air inlet 318 and is directed by air directing valve 319 todesiccant coated passive heat transfer device 320. Process air passesover the exposed surface of desiccant coated passive heat transferdevice 320, cooling and dehumidifying the air. Moisture from the air isadsorbed onto the desiccant, increasing the moisture content of thedesiccant. The heat of adsorption from the desiccant is transferred topassive heat transfer device 320 by conduction, and to the refrigerantflowing through. Sensible heat from the process airstream is alsotransferred to passive heat transfer device 320 and to the refrigerantflowing through. The cooled and dehumidified air is then blown throughair directing valve 322 by process fan 321, and passes through airoutlet 323 to the conditioned space 324.

Ambient air 325 from the environment enters outdoor device 303 throughinlet 326. Air passes over the exposed surface of passive heat transferdevice 305. Heat passes from the refrigerant to passive heat transferdevice 305, and from passive heat transfer device 305 to the air. Air isdrawn by fan 327 from passive heat transfer device 305 through outlet328 and back to the outdoor space 329.

FIG. 3B shows the second half-cycle of operation of system 300.Low-pressure refrigerant at a first pressure state enters compressor 304and is compressed to a second pressure state (e.g., high-pressure state)that is higher than the first pressure state. Refrigerant then flowsthrough uncoated passive heat transfer device 305, releasing some heatto ambient airstream 325. Refrigerant then flows through refrigerantline 306 from outdoor device 303 to indoor device 302. Refrigerant thenflows through reversing valve 307 (configured in a second valve state)and is directed to desiccant coated passive heat transfer device 320.Refrigerant then flows through desiccant coated passive heat transferdevice 320, releasing some heat to regeneration airstream 333.Refrigerant then flows through expansion valve 308, which takes therefrigerant from a high-pressure state to a low-pressure state.Refrigerant then flows through reversing valve 307 (in the second valvestate) and is directed to refrigerant line 335. Refrigerant flowsthrough refrigerant line 335 from indoor device 302 to indoor device301. Refrigerant then flows through uncoated passive heat transferdevice 310 absorbing heat from process air 312. Refrigerant then flowsthrough refrigerant line 311 from indoor device 301 to outdoor device303 and returns to compressor 304, completing the refrigerant circuit.

Process air 312 to be cooled enters indoor device 301 through air inlet313 and passes over the exposed surface of uncoated passive heattransfer device 310, cooling the air.

Regeneration air 333 enters indoor device 302 through inlet duct 332 andis directed by air directing valve 319 to desiccant coated passive heattransfer device 320. Regeneration air passes over the exposed surface ofdesiccant coated passive heat transfer device 320. Heat passes from therefrigerant to passive heat transfer device 320, and on to thedesiccant, causing desorption of moisture from the desiccant to thepassing air. In this way the desiccant is regenerated to begin the nextcycle. Regeneration air is then blown through air directing valve 322 byfan 321 and through outlet duct 331 to the outdoor space 330.

Ambient air 325 from the environment enters outdoor device 303 throughinlet 326. Air passes over the exposed surface of passive heat transferdevice 305. Heat passes from the refrigerant to passive heat transferdevice 305, and from passive heat transfer device 305 to the air. Air isdrawn by fan 327 from passive heat transfer device 305 through outlet328 and back to the outdoor space 329.

In some embodiments of system 300, indoor devices 301 and 302 may becombined within a common housing structure. Various embodiments arepossible with devices 301, 302, and 303 located inside or outside theconditioned space as separate devices or combined in a common housingstructure. In some operating modes of system 300, uncoated passive heattransfer device 310 may be operated below the dewpoint of process air312. Such an operating mode allows uncoated passive heat transfer device310 to dehumidify process air 312 as well as cooling it. In someembodiments, an additional expansion valve is added to refrigerant line335 between reversing valve 307 and uncoated passive heat transferdevice 310.

FIGS. 4A and 4B show schematic views of an exemplary desiccant coolingand dehumidification system 400. In operation, system 400 cycles betweentwo modes of operation: a first mode (also referred to as a firsthalf-cycle), and a second mode (also referred to as an a secondhalf-cycle). FIG. 4A illustrates the first mode of operation and 4Billustrates the second mode of operation. System 400 includes a heatpump comprising compressor 402, refrigerant reversing valve 403, firstdesiccant coated passive heat transfer device 406, expansion valve 405,and a second desiccant coated passive heat transfer device 404. System400 further includes first air directing valve 409, second air directingvalve 415, first fan 410, second fan 416, and air duct 419.

As shown in the example of FIGS. 4A and 4B, all components are locatedinside the conditioned space in one or more housing structures and formindoor device 401. The indoor space and outdoor space are separated bydividing wall 417. Indoor device 401 is physically connected to air duct419 which passes through dividing wall 417 to the outdoor space.

System 400 operates in a cyclic manner, alternating between two modes ofoperation, shown by FIGS. 4A and 4B. During the first half-cycle,desiccant coated passive heat transfer device 404 is in process mode anddesiccant coated passive heat transfer device 406 is in regenerationmode. During the second half-cycle, desiccant coated passive heattransfer device 404 is in regeneration mode and passive heat transferdevice 406 is in process mode.

FIG. 4A shows the first half-cycle of operation of system 400.Low-pressure refrigerant at a first pressure state enters compressor 402and is compressed to a second pressure state (e.g., high-pressure state)that is higher than the first pressure state. Refrigerant then flowsthrough reversing valve 403 (configured in a first valve state) and isdirected to desiccant coated passive heat transfer device 406.Refrigerant then flows through desiccant coated passive heat transferdevice 406 releasing some heat to regeneration airstream 413.Refrigerant then flows through expansion valve 405, which takes therefrigerant from a high-pressure state to a low-pressure state.Refrigerant then flows through desiccant coated passive heat transferdevice 404 absorbing some heat from process air 407. Refrigerant thenflows through reversing valve 403 (in the first valve state) and returnsto compressor 402, completing the refrigerant circuit.

Process air 407 to be cooled and dehumidified enters indoor device 401through air inlet 408. Process air passes over the exposed surface ofdesiccant coated passive heat transfer device 404, cooling anddehumidifying the air. Moisture from the air is adsorbed onto thedesiccant, increasing the moisture content of the desiccant. The heat ofadsorption from the desiccant is transferred to passive heat transferdevice 404 by conduction, and to the refrigerant flowing through.Sensible heat from the process airstream is also transferred to passiveheat transfer device 404 and to the refrigerant flowing through. Thecooled and dehumidified air is then drawn through air directing valve409 by process fan 410, and passes through air outlet 411 to theconditioned space 412.

Regeneration air 413 enters indoor device 401 through inlet duct 414.Regeneration air passes over the exposed surface of desiccant coatedpassive heat transfer device 406. Heat passes from the refrigerant topassive heat transfer device 406, and on to the desiccant, causingdesorption of moisture from the desiccant to the passing air. In thisway the desiccant is regenerated to begin the next cycle. Regenerationair is then drawn through air directing valve 415 by fan 416 and throughoutlet duct 418 to the outdoor space 419.

FIG. 4B shows the second half-cycle of operation of system 400.Low-pressure refrigerant at a first pressure state enters compressor 402and is compressed to a second pressure state (e.g., high-pressure state)that is higher than the first pressure state. Refrigerant then flowsthrough reversing valve 403 and is directed to desiccant coated passiveheat transfer device 404. Refrigerant then flows through desiccantcoated passive heat transfer device 404 releasing some heat toregeneration airstream 407. Refrigerant then flows through expansionvalve 405, which takes the refrigerant from a high-pressure state to alow-pressure state. Refrigerant then flows through desiccant coatedpassive heat transfer device 406 absorbing some heat from process air413. Refrigerant then flows through reversing valve 403 (configured in asecond valve state) and returns to compressor 402, completing therefrigerant circuit.

Process air 413 to be cooled and dehumidified enters indoor device 401through air inlet 414. Process air passes over the exposed surface ofdesiccant coated passive heat transfer device 406, cooling anddehumidifying the air. Moisture from the air is adsorbed onto thedesiccant, increasing the moisture content of the desiccant. The heat ofadsorption from the desiccant is transferred to passive heat transferdevice 406 by conduction, and to the refrigerant flowing through.Sensible heat from the process airstream is also transferred to passiveheat transfer device 406 and to the refrigerant flowing through. Thecooled and dehumidified air is then drawn through air directing valve415 by process fan 410, and passes through air outlet 411 to theconditioned space 412.

Regeneration air 407 enters indoor device 401 through inlet duct 408.Regeneration air passes over the exposed surface of desiccant coatedpassive heat transfer device 404. Heat passes from the refrigerant topassive heat transfer device 404, and on to the desiccant, causingdesorption of moisture from the desiccant to the passing air. In thisway the desiccant is regenerated to begin the next cycle. Regenerationair is then drawn through air directing valve 409 by fan 416 and throughoutlet duct 418 to the outdoor space 419.

In some embodiments of system 400, air inlets 408 and 414 are shared andthe process air splits to passive heat transfer devices 404 and 406after entering the device. In some embodiments of system 400, all orsome components of the device are located outside the conditioned spaceand achieve air exchange with the indoor space through additional ductsthrough dividing wall 417. In some embodiments of system 400, a secondduct through dividing wall 417 and two additional air directing valvesare included so in regeneration mode air is supplied from the outdoorspace instead of the indoor space.

In some embodiments of systems 100-400, a liquid-line suction line heatexchanger is used. The direction of airflow through the desiccant coatedpassive heat transfer devices shown schematically in systems 100-400 isarbitrary. Specifically, each system includes embodiments in which thedirection of airflow through the desiccant coated passive heat transferdevices is the same in both modes of operation (parallel flow) and inwhich the direction of airflow through the desiccant coated passive heattransfer devices reverses between the first and second modes ofoperation (counterflow).

FIGS. 5A through 5D shows details of two embodiments of refrigerant flowdirecting and metering device 208 in two modes of operation. FIG. 5Ashows embodiment A in mode 1. FIG. 5B shows embodiment A in mode 2. FIG.5C shows embodiment B in mode 1. FIG. 5D shows embodiment B in mode 2.Embodiment A is comprised of refrigerant check valves 502, 503, 506, and508, expansion valve 509, and refrigerant lines 501, 504, 505, and 507.Embodiment B is comprised of refrigerant check valves 510 and 515,expansion valves 511 and 514, and refrigerant lines 510, 514, 516, and517.

As shown in FIG. 5A, in mode 1 of embodiment A, high pressurerefrigerant enters the device through refrigerant line 501. Refrigerantpasses through check valve 502 and is blocked from passing through checkvalve 503. Refrigerant flows out of device 208 through refrigerant line504. High pressure refrigerant enters the device through refrigerantline 505, then passes through expansion valve 509, which takes therefrigerant from a high-pressure state to a low-pressure state. Lowpressure refrigerant then passes through check valve 506 and is blockedfrom passing through check valve 508. Refrigerant then flows out ofdevice 208 through refrigerant line 507.

As shown in FIG. 5B, in mode 2 of embodiment A, high pressurerefrigerant enters the device through refrigerant line 507. Refrigerantpasses through check valve 508 and is blocked from passing through checkvalve 506. Refrigerant flows out of device 208 through refrigerant line504. High pressure refrigerant enters the device through refrigerantline 505, then passes through expansion valve 509, which takes therefrigerant from a high-pressure state to a low-pressure state. Lowpressure refrigerant then passes through check valve 503 and is blockedfrom passing through check valve 502. Refrigerant then flows out ofdevice 208 through refrigerant line 501.

As shown in FIG. 5C, in mode 1 of embodiment B, high pressurerefrigerant enters the device through refrigerant line 517. Refrigerantpasses through check valve 510. Refrigerant flows out of device 208through refrigerant line 512. High pressure refrigerant enters thedevice through refrigerant line 513. Refrigerant is blocked from passingthrough check valve 515 and passes through expansion valve 514, whichtakes the refrigerant from a high-pressure state to a low-pressurestate. Low pressure refrigerant then flows out of device 208 throughrefrigerant line 516.

As shown in FIG. 5D, in mode 2 of embodiment B, high pressurerefrigerant enters the device through refrigerant line 516. Refrigerantpasses through check valve 515. Refrigerant flows out of device 208through refrigerant line 513. High pressure refrigerant enters thedevice through refrigerant line 512. Refrigerant is blocked from passingthrough check valve 510 and passes through expansion valve 511, whichtakes the refrigerant from a high-pressure state to a low-pressurestate. Low pressure refrigerant then flows out of device 208 throughrefrigerant line 517.

FIGS. 6A and 6B show two modes of operation of one embodiment of anindoor unit of system 100, 200, 300, or 400 in cross-section view. Inthis embodiment the desiccant coated passive heat transfer device is afin-and-tube heat exchanger with desiccant partially coated on the finsof the heat exchanger, and the fan is a crossflow fan.

As shown in FIG. 6A, in mode 1 heat exchanger 604 is in process mode.Return air 601 from the conditioned space enters device 600 throughopening 602 and passes through air directing valve 603 in a firstposition to heat exchanger 604. The air is first exposed to the uncoatedfin surface 610, cooling the air. At surface 610, sensible heat istransferred from the air to heat exchanger 604 and to the refrigerantflowing through. The air is then exposed to desiccant coated fin surface605, cooling and dehumidifying the air. At surface 605, moisture fromthe air is adsorbed onto the desiccant, increasing the moisture contentof the desiccant. The heat of adsorption from the desiccant istransferred to heat exchanger 604 by conduction, and to the refrigerantflowing through. Sensible heat from the process airstream is alsotransferred to heat exchanger 604 and to the refrigerant flowingthrough. Air is then drawn through crossflow fan 606 and passes by airdirecting valve 607 in a first position through opening 608 to theconditioned space 609.

As shown in FIG. 6B, in mode 2 heat exchanger 604 is in regenerationmode. Outdoor air 614 enters device 600 through opening 611 and passesthrough air directing valve 603 in a second position to heat exchanger604. The air is first exposed to the uncoated fin surface 610, heatingthe air. At surface 610, sensible heat is transferred from refrigerantflowing through heat exchanger 604 to the exposed surface 610 and onwardto the air. The air is then exposed to desiccant coated fin surface 605,heating and humidifying the air. At surface 605, heat is transferredfrom refrigerant flowing through heat exchanger 604 to the desiccantcoated on surface 605 causing desorption of moisture from the desiccantto the passing air. Air is then drawn through crossflow fan 606 andpasses by air directing valve 607 in a second position through opening612 to the outdoor space 613.

In some embodiments of device 600 an additional operation mode allowsoutdoor air to be drawn from ambient air 614 through opening 611 whileheat exchanger 604 is in process mode to cool and ventilate theconditioned space.

In the examples described above, at least a portion or an entire surfaceof any of the passive heat transfer device(s) described above can be atleast partially or completely coated with a desiccant material accordingto various examples. In one example, a surface of the passive heattransfer device can be between at least one tenth covered (e.g., 10%covered) and up to completely covered (100% covered) with desiccantmaterial, or any coverage value in between the described range.

FIG. 7 depicts a method of control for a desiccant cooling anddehumidification system as described in the examples above. In anexample, the method can be implemented by a process(or) and anon-transitory storage medium (e.g., memory) having instructions storedthereon and configured to be executed by the processor. Upon startup701, the system measures the temperature and humidity of the indoor andoutdoor space 702. These measurements are used to set system parametersfor a default operating mode 703. During default operating mode, thetemperature and humidity at the inlet and outlet of each desiccantcoated passive heat transfer device is measured. After some time, thedesiccant of the process stream will become saturated and the rate ofmoisture removal from the process airstream will decrease. At this time,the outlet humidity ratio will approach the inlet humidity ratio. Thecontrol system logs this as the required desiccant load time 704.Similarly, after some time, the desiccant of the regeneration streamwill become desaturated, and the rate of moisture addition to theregeneration airstream will decrease. At this time, the outlet humidityratio will approach the inlet humidity ratio. The control system logsthis as the required desiccant unload time 704.

While the system is running in default mode 703, the indoor temperatureand humidity are measured over time, and the sensible and latent loadare determined 705. In one operating mode, sensible cooling is adjustedto match sensible load, and latent cooling is adjusted to match latentload. In one embodiment, sensible cooling is adjusted by modulatingprocess fan speed. In one embodiment, latent cooling is adjusted bymodulating the process duty cycle, defined as the required loading timeover the switching time. In a preferred operating mode, the requireddesiccant unload time is modulated to equal the switching time bycontrolling the compressor speed and regeneration fan speed.

The foregoing has been a detailed description of illustrativeembodiments of the invention. Various modifications and additions can bemade without departing from the spirit and scope of this invention.Features of each of the various embodiments described above may becombined with features of other described embodiments as appropriate inorder to provide a multiplicity of feature combinations in associatednew embodiments. Furthermore, while the foregoing describes a number ofseparate embodiments of the apparatus and method of the presentinvention, what has been described herein is merely illustrative of theapplication of the principles of the present invention. For example, asused herein, the terms “process” and/or “processor” should be takenbroadly to include a variety of electronic hardware and/or softwarebased functions and components (and can alternatively be termedfunctional “modules” or “elements”). Moreover, a depicted process orprocessor can be combined with other processes and/or processors ordivided into various sub-processes or processors. Such sub-processesand/or sub-processors can be variously combined according to embodimentsherein. Likewise, it is expressly contemplated that any function,process and/or processor herein can be implemented using electronichardware, software consisting of a non-transitory computer-readablemedium of program instructions, or a combination of hardware andsoftware. Additionally, as used herein various directional anddispositional terms such as “vertical”, “horizontal”, “up”, “down”,“bottom”, “top”, “side”, “front”, “rear”, “left”, “right”, and the like,are used only as relative conventions and not as absolutedirections/dispositions with respect to a fixed coordinate space, suchas the acting direction of gravity. Additionally, where the term“substantially” or “approximately” is employed with respect to a givenmeasurement, value or characteristic, it refers to a quantity that iswithin a normal operating range to achieve desired results, but thatincludes some variability due to inherent inaccuracy and error withinthe allowed tolerances of the system (e.g. 1-5 percent). Accordingly,this description is meant to be taken only by way of example, and not tootherwise limit the scope of this invention.

What is claimed is:
 1. An air-handling system comprising: a heat pumpconfigured to move heat energy between a plurality of passive heattransfer devices; the plurality of passive heat transfer devices,defining a first surface of at least one of the plurality of passiveheat transfer devices that is thermally in contact with the heat pumpand a second surface of at least one of the plurality of passive heattransfer devices that is exposed to allow the transfer of heat to orfrom the heat pump; a desiccant in thermal contact with the exposedsurface of at least one passive heat transfer device and configured toexchange moisture with air; a plurality of air directing valvesconfigured to direct process and regeneration air to and from theplurality of passive heat transfer devices with desiccant; a heat pumpreversing device configured to change the direction of heat flow in theheat pump between two modes of operation; a control system withcommunication lines to control air directing valves, reversing device,and heat pump operation; and a control operation process operating acontrol mode in which desiccant regeneration time is modulated.
 2. Thesystem of claim 1 wherein the passive heat transfer devices comprisetube and fin heat exchangers or microchannel heat exchangers.
 3. Thesystem of claim 2 wherein the desiccant forms a coating on the exposedsurface of the heat exchanger fins.
 4. The system of claim 3 wherein thedesiccant forms a partial coating with an uncoated section first exposedto airflow followed by a desiccant coated second section exposed toairflow.
 5. The system of claim 1, further comprising, a passive heattransfer device without desiccant configured for exchanging sensibleheat with ambient air.
 6. The system of claim 1, further comprising, apassive heat transfer device without desiccant configured for exchangingsensible heat with indoor air.
 7. The system of claim 1 wherein thedesiccant comprises at least one of silica gel, alumina, zeolite or ametal-organic framework (MOF) material.
 8. A method for handling air ina space comprising the steps of: moving, with a heat pump, heat energybetween a plurality of passive heat transfer devices, in which a firstsurface of at least one of the plurality of passive heat transferdevices is thermally in contact with the heat pump and a second surfaceof at least one of the plurality of passive heat transfer devices isexposed to allow the transfer of heat to or from the heat pump;providing a desiccant in thermal contact with the exposed surface of atleast one passive heat transfer device and configured to exchangemoisture with air; directing, through a plurality of air directingvalves, process and regeneration air to and from the plurality ofpassive heat transfer devices with desiccant; changing a direction ofheat flow in the heat pump between two modes of operation; andcontrolling the plurality air directing valves, reversing device, andheat pump operation in a control operation mode to modulate desiccantregeneration time.
 9. The method of claim 8 wherein the passive heattransfer devices comprise tube and fin heat exchangers or microchannelheat exchangers.
 10. The method of claim 9 wherein the desiccant forms acoating on the exposed surface of the heat exchanger fins.
 11. Themethod of claim 10 wherein the desiccant forms a partial coating with anuncoated section first exposed to airflow followed by a desiccant coatedsecond section exposed to airflow.
 12. The method of claim 8, furthercomprising, exchanging, using a passive heat transfer device withoutdesiccant, sensible heat with ambient air.
 13. The method of claim 8,further comprising, exchanging, using a passive heat transfer devicewithout desiccant, sensible heat with indoor air.
 14. The method ofclaim 8 wherein the desiccant comprises at least one of silica gel,alumina, zeolite or a metal-organic framework (MOF) material.